This invention relates to laminated collapsible dispensing tubes and in particular such tubes formed from a laminate which includes two separate layers of metallic foil.
Until recently the majority of commercially used collapsible dispensing tubes have been constructed of lead and other similar materials. Lead in particular has a unique combination of characteristics making it well suited for use in such a tube. It is reasonably rigid thereby affording protection to the product contained in a tube formed of it while being deformable enough to allow it to be rolled-up. In addition lead has an extremely low yield point and consequently will stay in the rolled-up position.
Two of the major characteristics used in describing collapsible dispensing tubes is their "body" which is the feeling of substantialness of the tube and which can best be measured by the force required to roll up the tube and the "deadfold" of the tube which is its tendency to remain in the rolled-up position. As mentioned previously, lead tubes have both good body and good deadfold and the consumer's familiarity with them has made them the standard against which other tubes are measured in respect to these properties.
Lead tubes have certain disadvantages such as their tendency to crack and their requirement for coating them to make them compatible with certain products which they may contain. Consequently there has been a continuing search for acceptable substitutes for lead tubes.
Various polymers, i.e. plastic materials, were considered as possible replacements for lead tubes. Plastic materials however do not have the required low yield point to give the tube an appropriate degree of deadfold. In addition, plastic materials are not impervious to oxygen and water vapor transmission thereby making them unacceptable for packaging many commercial products, e.g. toothpaste.
Various laminate structures have therefore been tried as a substitute for lead tubes. In the design of such laminate structures each layer of material has generally been considered as a means for accomplishing a single purpose, for example, a single layer of metallic foil is frequently used as the main structural unit of the tube. Additional layers of material have then been added to provide various barrier properties or to provide an appropriate surface on which printing can be done. Similarly, other materials each performing a single function are added to form an overall laminate structure some of which have had as many as eight separate layers.
As the result of the approach of considering each layer of a laminate tube separately as the prior art does, such tubes have heretofore had a number of inherent compromises principally as a result of inability to independently vary deadfold and body.
It has been found that a laminate structure containing two layers of metallic foil permits variation in deadfold and body properties substantially independently of one another and therefore allows the production of a collapsible dispensing tube with both desirable deadfold and body properties. In addition, the tube of this invention has the ability to achieve both of these results while using reduced amounts of the relatively expensive metallic foil.